[pianotech] Bolduc glue

[Delwin D Fandrich]

See below:

Delwin D Fandrich
Piano Design & Fabrication
6939 Foothill Court SW, Olympia, Washington 98512 USA
Phone  360.515.0119 — Cell  360.388.6525
del at fandrichpiano.com — ddfandrich at gmail.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Friday, February 24, 2012 12:44 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Bolduc glue

On 2/24/2012 2:04 PM, Delwin D Fandrich wrote:
>And I have to confess--please don't tell the glue  police!--I've used 
>Titebond II to glue up more than one vertically laminated  bridge body 
>and, as far as I know, twenty and thirty years later they  haven't yet 
>come apart or straightened out.

And I don't consider it a confession at all that I have built a number of
curved laminated cutoff bars and vertically laminated horizontally capped
bridges with Titebond original with similar disastrous results.

-- Yes, I forgot about those cutoff bars. Hard maple, relatively thick stuff
and a nice curve and all put together with good old Titebond.



>I doubt this would be a
> problem once the belly structure was fully assembled but until then 
>I'd  think spring-back might be a problem. It would be an interesting 
>experiment  and I might well be surprised. It wouldn't be the first time.

Spring back is definitely a problem in those cutoff bars and bridges if they
are pulled out of the caul too soon. Again, cycle time. I tend to turn the
lights out on wet glue in the evening whenever I can, and in these cases I
take all but a few strategic clamps off in the morning, and leave these on
and the assembly in the caul for another day or two. 
Once adequately dry, spring back is nearly nonexistent.

-- That is the key; let the stuff dry thoroughly. The mistake made by many
is pulling the thing from the caul too soon. It can take a really long time
for the moisture way down in the middle of a thick, heavy maple bent
laminate part to work its way out. Far longer than seems reasonable at first
blush. But water is the solvent here and to get out it has to work its way
slowly through the body of the piece. Spruce rib stock I'll take out after a
day or so. Cutoff bars I make of sawn maple and I'll leave them clamped up
for at least three days. Years back when I was first starting to do this
stuff I took one out too soon (If memory serves I laid it up last thing at
night and I took it out the next morning.) and it looked fine at first but
some hours later it had straightened out enough that I didn't want to use
it. I sliced it open and measured the moisture content at the middle of the
thing. I don't remember the numbers now but I do remember being really
surprised at just how high it was. No wonder it wanted to straighten out;
the glue inside the body of the thing wasn't fully dry yet.



> I may have some additional information somewhere. If I come up with 
> anything I'll add it to the list. But I don't think I've ever seen a 
> Shore hardness rating for any adhesive....

Me either, yet the mythology insists that one must have a glass hard glue
for belly work, yet such a designation isn't quantified on any adhesive. Nor
is a quantification for the dreaded creep. Sounds like just another typical
piano specification doesn't it?
Ron N

-- Ah, but mythology always sells better than cold, hard reason and logic.
If the steak is tough, sell the sizzle.

ddf